I saw a couple of people using them on our last cruise but not enough to make it annoying. Princess does rent them by the day but it's more economical to just buy a set. I always got so-so results using mine. I always give my wife my schedule so if she really needs me she knows where to look.

We use them everytime. Sometimes when you're trying to reach someone in the bowels of the ship, say the 3rd floor, and you're up on the pool deck on the 12th deck you may get a lot of interferance, we've not had too many problems. I highly reccommend them, especially if you have kids. There are so many activities on the larger ships, the radios make it real easy to stay connected, otherwise you'll spend your day wondering what happened to the others. Buy them beforehand. They usually sell them on the ship in the gift shop if you forget, but they're much more expensive. Have a great cruise!